<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <div class="main">123</div>
    <script src="./jquery.js"></script>
    <script>
        new jQuery(".main").append("这是测试文字");
    </script>
</body>
</html>